deva report

A

Seminar Report

on

Wind Turbine LightningProtection

Submitted By:

Borase Devendra Vijayrao

B.E. [Department of Mechanical Engineering]

Guided By:

Prof.V.M.Patil

Department of Mechanical Engineering

R. C. Patel Institute of Technology,

Shirpur-425405

2016-17

Shirpur Education Society’s

R. C. Patel Institute of Technology,Shirpur, Dist-Dhule

CERTIFICATE

This is to certify that Borase devendra Vijayrao

from B.E[Mechanical Engineering] has satisfactorily car-

ried out seminar work on “Wind Turbine Lightning

Protection” and submitted the report in the premises of

Department of Mechanical Engineering under the guid-

ance of Prof.V.M.Patil during year 2016-2017.

Date:

Place: Shirpur

Seminar Guide Coordinator

Head of Department Principal

Acknowledgement

I take this opportunity to express my heartfelt gratitude towards the Depart-

ment of Mechanical Engineering, RCPIT, Shirpur that gave me an opportunity for

presentation of my seminar in their esteemed organization.

It is a privilege for me to have been associated with Prof.V.M.Patil, my guide

during seminar work. I have been greatly benefited by her valuable suggestion and

ideas. It is with great pleasure that I express my deep sense of gratitude to her for

her valuable guidance, constant encouragement and patience throughout this work.

I express my gratitude to Prof.N.P.Salunke[Head Of Department] for his con-

stant encouragement, co-operation and support and also thankful to all people who

have contributed in their own way in making this seminar success.

I take this opportunity to thank all the classmates for their company during the

course work and for useful discussion I had with them.

Under these responsible and talented personalities I was efficiently able to com-

plete my seminar in time with success.

Borase Devendra Vijayrao

Abstract

The lightning protection standards describe how wind turbine blades should be

protected from the tip and down to radius 20m, whereas only a few evidences of

such exposure has been presented. Both numerical simulations as well as extensive

field data provide evidence that the direct strike exposure is focused on the tip of

the blade, and that the peak current of strokes expected inboard are of limited

amplitude. This has led to the Lightning Zoning Concept for blades, as well as a

revised approach of the Exposure Risk assessment which is treated in the present

paper. In 2015 a zoning concept for lightning protection of wind turbine blades was

published, refined slightly in 2015. The Zoning concept was developed to present an

engineering tool for assessing which lightning strikes that attaches to the different

regions of the blade. In the present paper, this Zoning concept is revised based on

more recent analysis and field investigations, and defines regions of the blade that

would be exposed to certain peak currents

Contents

List of Figures iii

1 Introduction 11.1 Types of wind turbine . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Horizontal Axis Wind Turbine . . . . . . . . . . . . . . . . . . 11.1.2 Vertical axis wind turbine . . . . . . . . . . . . . . . . . . . . 2

1.2 lightning and its effect . . . . . . . . . . . . . . . . . . . . . . . . . . 41.2.1 What is lightning . . . . . . . . . . . . . . . . . . . . . . . . . 41.2.2 DIRECT EFFECTS (strikes on structures) . . . . . . . . . . 41.2.3 INDIRECT EFFECTS (network overvoltages) . . . . . . . . . 5

2 Literature Survey 6

3 Grounding, Bonding, Surge protection Lightning protection 83.1 Critical elements of blade lightning system Conductor Technology . . 8

3.1.1 Permanent, Low-Impedance Connections . . . . . . . . . . . . 93.1.2 Receptor Attachment . . . . . . . . . . . . . . . . . . . . . . . 10

4 Wind turbine protection 124.1 Composition of the Turbine Blade with Lightning Protection . . . . 124.2 Shielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.3 VPC Protection (uptower control box) . . . . . . . . . . . . . . . . . 134.4 Base Controller Protection . . . . . . . . . . . . . . . . . . . . . . . . 144.5 Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154.6 Existing Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.6.1 Standard for the Installation of Lightning Protection Systems,NFPA 780 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.6.2 Protection of Structures Against Lightning, IEC 61024 . . . . 164.6.3 The Assessment of Risk Due to Lightning, IEC 61662 . . . . 164.6.4 Protection Against Lightning Electromagnetic Impulses, IEC

61312 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.6.5 Grounding of Industrial and Commercial Power Systems,

IEEE 142- 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . 17

i

5 Advantages and disadvantages of wind mill 18

Conclusion 20

References 21

ii

List of Figures

1.1 Fig:Horizontal Axis and Vertical axis wind turbine . . . . . . . . . . 21.2 Fig:Nomenclature of the wind turbine . . . . . . . . . . . . . . . . . 41.3 Fig:Effects of lightning . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.1 Fig:Critical elements of blade lightning system Conductor Technology 93.2 Fig:Permanent, Low-Impedance Connections . . . . . . . . . . . . . 103.3 Fig:Receptor Attachment . . . . . . . . . . . . . . . . . . . . . . . . 11

iii

Chapter 1

Introduction

WIND TURBINE :- A wind turbine is a device that converts the wind’s

kinetic energy into electrical power.

1.1 Types of wind turbine

1.1.1 Horizontal Axis Wind Turbine

A horizontal Axis Wind Turbine is the most common wind turbine design. In

addition to being parallel to the ground, the axis of blade rotation is parallel to the

wind flow.

A)up wind turbine Some wind turbines are designed to operate in an upwind mode

(with the blades upwind of the tower). Large wind turbines use a motor-driven

mechanism that turns the machine in response to a wind direction. Smaller wind

turbines use a tail vane to keep the blades facing into the wind.

B)down wind turbine Other wind turbines operate in a downwind mode so that the

wind passes the tower before striking the blades. Without a tail vane, the machine

rotor naturally tracks the wind in a downwind mode.

1

RCPIT, Shirpur Department of Mechanical Enggineering

Figure 1.1: Fig:Horizontal Axis and Vertical axis wind turbine

1.1.2 Vertical axis wind turbine

Although vertical axis wind turbines have existed for centuries, they are not as

common as their horizontal counterparts. The main reason for this is that they do

not take advantage of the higher wind speeds at higher elevations above the ground

as well as horizontal axis turbines.

Nomenclature of wind turbine

• Blade:- Most turbine have three blades. The turning of blades generate elec-

tricity.

• Hub :- Centre of the rotor to which the rotor blades are attached.

• Rotor:- Blade and hub referred together.

• Gears:- Connects low speed shaft to high speed shaft and increases rotational

speeds from 30 to 60 rpm to about 1000to 1800 rpm.

• Generator:- Device which produce electricity.

Wind Turbine Lightning Protection 2


• Controller:- Starts up and shuts of the machine.

• Anemometer:- Measure wind speed and Transmit wind speed data to con-

troller.

• Wind wane:- Measure wind direction and communicates with yaw drive to

orient the turbine.

• Yaw drive:- Keep rotor facing into the wind as wind direction changes.

• Nacelle:- Contain gear box, low and high speed shafts, generator, controller

and brakes.

• Tower:-Made from tubular steel, concrete or steel lattice. Taller tower generate

more power.

• Pitch:-Blades are turned, or pitched, to control rotor speed.

• Brake:- Stops rotor In emergencies.



Figure 1.2: Fig:Nomenclature of the wind turbine

1.2 lightning and its effect

1.2.1 What is lightning

Lightning is a sudden electrostatic discharge that occurs during an electrical storm.

This discharge occurs between electrically charged regions of a cloud (called intra-

cloud lightning or IC), between that a cloud and another cloud (CC lightning), or

between a cloud and the ground (CG lightning).

1.2.2 DIRECT EFFECTS (strikes on structures)

At the point of the strike, lightning generates: - Direct thermal effects (melting,

fire) caused by the electric arc - Thermal and electrodynamic effects induced by

circulation of the lightning current - Blast effects (shock wave and blast air) produced

by heat and the expansion of the air. Protection against the direct effects of lightning

is based on catching the current and discharging it to earth (lightning conductor,



Figure 1.3: Fig:Effects of lightning

catcher rods, etc).

1.2.3 INDIRECT EFFECTS (network overvoltages)

Overvoltages due to lightning can reach the installation by three means of access: -

By conduction following direct lightning strikes on lines (power, telecommunications,

TV, etc.) entering or exiting buildings.


Chapter 2

Literature Survey

McElroy et al.[1], Mongolia, sandwiched between Russia and China, has

a high potential for wind-powered energy. As an emerging and developing country

with a large land size, Mongolia is an excellent choice for renewable energy practices,

according to McElroy at al. (2009). Currently, coal is used as the major source of

energy in the area because it is abundant and cheap. However, with the advancement

of wind turbine technology and its widespread use and production, wind powered

energy is becoming a cost effective way to harness energy sustainably . A sustainable

energy resource is one that can be used renewably over our lifetimes and brings little

to no impact on our worlds ecosystems.

Khushrushahi et al [2], Currently, according to Noushin Khushrushahi

et at. (2006), Mongolia receives the majority of energy from coal-powered plants.

Coal is a readily available fuel because nearly half of Mongolia is a coal basin. This

makes coal very easy to obtain and very cheap for energy generation. Because

Mongolia uses so little energy (compared to developed nations), most people see

little sense in changing to a more expensive and harder to install renewable energy.

Up to eighty percent of Mongolias energy is from coal and the remaining comes

mostly from hydroelectric generators. To date, Mongolia uses just under 800 MW

of energy but is steadily increasing their need for energy. In theory, the cheapest

and easiest way for Mongolia to obtain more power would be to import their energy

from China.

6


Zervos et.al [3], the Asian market added nearly one third of the total

new wind generators installed worldwide in 2008. In total, 36.5 billion (50 billion)

was spent on turbine instillations worldwide that year. Almost half a million people

are employed in some way by the wind energy industry and that number is growing

steadily. With the current use of wind energy, over 158 million tons of carbon

dioxide are saved from entering the atmosphere annually. Today, the United States

leads with the world in wind energy generation, producing over 25,000 MW . Wind

energy is now being produced world-wide and developing nations have began turning

to wind powered renewable energy.


Chapter 3

Grounding, Bonding, Surge

protection Lightning protection

3.1 Critical elements of blade lightning system

Conductor Technology

Lightning protection conductors are designed and manufactured to meet specific

criteria for an effective and reliable conduction of lightning currents. For optimal

performance, the conductors must maintain the following characteristics:

• Low inductance per unit length

• Low surge impedance Current-carrying capability to withstand, without degra-

dation, the thermal and mechanical effects of lightning

• Resistance to environmental effects When applied to applications with wind

turbine blades, the construction and design of the blade may require additional

characteristics for the conductors. Insulation, splicing and termination meth-

ods adequate to contain the lightning energy under current impulse conditions

8


Figure 3.1: Fig:Critical elements of blade lightning system Conductor Technology

• Ability to withstand mechanical fatigue over time The application of optimal

conductors within wind turbine blades is both unique and often complicated,

and varies from one blade design and construction to another. ERICOs ex-

tensive knowledge and experience within this industry make it ideally suited

to face these challenges. By manufacturing a wide selection of lightning con-

ductor solutions in multiple facilities around the world, ERICO can provide

the high-quality, innovative products and services you require to consistently

meet your needs.

3.1.1 Permanent, Low-Impedance Connections

It is Who We Are Connections are often considered the weakest point of an electrical

circuit and this is especially true in the protection scheme within a wind turbine

blade. They are subject to constant vibration and corrosion, as well as the thermal

and mechanical stresses that are present during a lightning event. In addition, it is

difficult to inspect or test the electrical connections within a blade after the system

has been installed. Experience has shown that the most effective protection schemes

over time are designed and manufactured with permanent connections, which helps

to ensure the system can handle a variety of adverse conditions.



Figure 3.2: Fig:Permanent, Low-Impedance Connections

Since 1938, ERICO has specialized in making electrical connections that will

never loosen, corrode or increase in resistance. Because of the affordability, success

and superiority of the CADWELD welded electrical connection, ERICO is consid-

ered a world leader in the development of high-current electrical grounding connec-

tions that are suitable for the harshest environments. ERICO also manufactures

a vast array of methods that are used to connect conductors within wind turbine

blades. These methods are designed and tested to meet the CENELEC EN50561

standard and other national standards, such as UL 96. Whether the protection

scheme requires an insulated connection, connections to receptors, or connections

from conductor to conductor, you can trust ERICO to have the right connection

method for your specifi c application.

3.1.2 Receptor Attachment

To continuously enhance its lightning protection process, ERICO has conducted

years of research involving long-term fi eld studies and has performed laboratory

testing using some of the largest outdoor test laboratories available. Countless

research study programs, including joint ventures with accomplished scientists in the

fi eld, have also been used in its research process. This extensive research program

has resulted in some of the most up-to date, published technical papers and journals,



Figure 3.3: Fig:Receptor Attachment

including patents in this area. ERICO is also committed to the development and

harmonization of lightning protection standards around the world. The placement

of receptors on structures, such as wind turbine blades, is performed using statistical

models. A risk management approach is required to determine the receptor number

and placement to provide optimum protection. The design of the receptor itself

also infl uences its ability to capture the lightning. ERICO can provide receptors

based on the material type, design and size of the blade. Years of experience and

knowledge in the fi eld of lightning protection, combined with global manufacturing

capabilities, make ERICO a premier source for providing comprehensive protection

solutions. ERICO can also manufacture the required products and hardware to

update existing systems.


Chapter 4

Wind turbine protection

4.1 Composition of the Turbine Blade with Light-

ning Protection

1.1 Construction of these 1.5MW turbine generator blades are fibreglas epoxy resin

with an exterior gel coat. The blade interior structure is spar-reinforced with rigid

polyurethane foam encased in fiberglass. Further interior strength is via sandwich

sheets of urethane/fibreglas/urethane/fibreglas in built-up layers. It is not within

the scope of this study to examine the cellular nature, sheer strength or other phys-

ical characteristics of urethane foam. However, crude experiments at the wind farm

showed water was absorbed into urethane samples.

1.2 Lightning protection consists of several exterior copper receptor air termination

discs, which are fastened to interior aluminum conductors running the length of

the blade. Conductors are fastened to the blade and to one another with steel

bolts. Near the blade root a portion of the conductor is imbedded into the fibreglas.

The conductor transitions from the blade root area via bonding to the hub and

thence to a ground reference. Other components of the lightning protection systems

were examined briefly. The manufacturer provided satisfactory surge protection for

sensitive electronics. Grounding requirements were completed per manufacturers

specifications by the installation contractor.

12


4.2 Shielding

• The nacelle cover is glass reinforced polyester (GRP) with no metal content.

No shielding is associated with this.

• The steel tower should be the first level of shielding. As soon as wires enter

the tower, no further shielding is needed because the lightning current will be

conducted by the metallic tower to the earth. As such, the shields and ground

wires should be terminated on entry to the tower (i.e., at droop wire clamp

below gearbox).

• The steel variable pitch controller (VPC) box is the first level of shield for

any sensors that conduct to it or any controller cards or devices inside it. LTI

recommends terminating shields at both ends (i.e., at the sensor and the VPC

box).

• Control and sensor wire shields and braids should be terminated at both the

VPC and the base controller.

• At any exposed areas in nacelle, sensors should also have an overbraid covering

the wires. (In places where the termination of sensor shield wire causes any

signal problems, remove the shield at the sensor but ensure that overbraid is

complete from sensor to VPC.)

4.3 VPC Protection (uptower control box)

• All sensors go down to the motherboard via the VPC terminal strip.

• Sensor shields are not grounded at the VPC. They are made common to other

shields and continued to base. This is bad practice because the combined

shields may cause coupling between sensors.

• Not all shields are terminated at base. Those that are terminate only at the

ground strip (bottom center of control box). They should be terminated as



soon as they enter box.

• The VPC box is not bonded to turbine frame or anywhere else. It is mounted

on rubber vibration mounts that stand the box off from the gearbox by about

19 mm (0.75 in.) (see Figure 11). The ground path is assumed to be in

sensor or control wires and shields to sensor housings or base controller. It

is recommended that the VPC be bonded to the local frame in at least two

places.

• No surge protection is offered to any sensors, the operator interface terminal

(OIT), or the modem that negotiates communication with the motherboard

in the downtower control box. It was unclear if there is surge protection on

the PC boards.

4.4 Base Controller Protection

• Ground bus on the 480 VAC side of box is on insulated standoffs, and at

no point is it connected to the control box. It is recommended that this be

bonded directly to the control box, making the whole control box the single

point ground (SPG).

• The sensor terminal strip should have direct-mounted lugs for grounding shields

to box. Currently they must travel to the terminal strip, through wireways to

the un-bonded ground bus, and finally into the rebar. Bonding these shields

directly at the entry to the box keeps unwanted current arriving in the shield

from being conducted inside the box along other control wires in the wire-way

• An isolation board is between most sensors and the controller card rack. This

appears to be optoisolation and signal conditioning for temperature probes

and other sensors.

• Custom 120 kA surge suppressors are installed at the three phase terminals

(to SPG) in the controller and at the terminals in the generator junction box.



4.5 Grounding

The grounding details are described for a typical turbine in Figure 13 and Figure

14. The grounding electrode was significantly modified with a retrofit designed by

Rich Kithill at the National Lightning Safety Institute (NLSI). Some observations

of the details follow:

• Each of the four tower legs are tied to a ground wire inside the concrete pier

(Ufer ground).

• Each tower leg is connected by copper braid to a ring electrode [30.5 m (100

ft) of 2/0].

• Two of the tower legs are connected by 2/0 copper braid to 46 m (150 ft) of

38 mm (1.5 in.) copper strap buried in irrigated bentonite laid out in 0.9 x 15

m (3 x 50 ft) radial crow’s feet (irrigated twice a month).

• All 3 phases of the 25 kV buried site feeder has a common braid terminated

at each turbine transformer box (primary side).

• The air terminal (lightning rod) on the nacelle has insulated 4/0 Cu welding

cable conducting to the ground braid (no bond to tower).

• The generator J-Box (generator ground) is connected by insulated 4/0 Cu

conductor to a tower bond 1.5 m (5 ft) from base (below sensor) and control

box.

• The controller path to ground is either via the neutral cable or via the feeder

transformer box into a ground rod and the ring electrode.

• The controller and uptower generator surge protection device clamps to SP

ground.



4.6 Existing Standards

4.6.1 Standard for the Installation of Lightning Protection

Systems, NFPA 780

NFPA 780 9 is from the standards group that maintains the National Electric Code,

and it is geared to installation details. However, this has little bearing in the pro-

tection of wind turbines because it is focused specifically on buildings and similar

structures. In fact, in the scope electric generating, transmission, and distribution

systems are specifically excluded.

4.6.2 Protection of Structures Against Lightning, IEC 61024

IEC 61024 10 is the primary standard for lightning protection of structures in Eu-

rope. The International Electrotechnical Commission maintains this and other light-

ning specific standards under TC81. It is an extremely useful document for design

and maintenance of lightning protection systems. This is especially true with siz-

ing down-conductors and ground electrodes. There is also good rationale for using

structural metal as natural conductors. Specific to wind turbines, the standard (as

of 1999) has not addressed tall structures those above 60 meters (196.8 feet) are

excluded. Also, in the scope electric generating, transmission, and distribution sys-

tems external to a structure are excluded. Nonetheless, the standard is a strong

design tool for general lightning protection.

4.6.3 The Assessment of Risk Due to Lightning, IEC 61662

IEC 61662 11 is used to assess the risk of lightning damage in terms of personnel

safety or cost. Procedures are provided to perform these analyses.



4.6.4 Protection Against Lightning Electromagnetic Im-

pulses, IEC 61312

IEC 61312 12 is a five part standard focused on protecting against damage to com-

munication and other low voltage systems. The use of lightning protection zones,

as a first line of defense, is well defined in Part 1. In fact, it is suggested that light-

ning protection systems can be made quite robust and efficient if Surge protection

devices are discussed thoroughly in Part 3 and somewhat in Part 1. Part 1 also has

a useful appendix on the waveforms that are expected at an installation and the

fundamental differences with waveforms used to test devices.

4.6.5 Grounding of Industrial and Commercial Power Sys-

tems, IEEE 142- 1991

IEEE 142 23 is somewhat outdated, but it describes good practices for any power

system especially those contained completely by a building. It is concerned with

primarily 60 Hz fault safety.


Chapter 5

Advantages and disadvantages of

wind mill

• Renewable energy

• Pollution free

• Cost effective

• Does not use water

• No fuel charges

Disadvantages

• Causes death to wildlife, such as birds and bats

• Wind turbine cannot build anywhere

• Generate noise, some people does not like

• Wind is not always predictable

18

Conclusion

Wind turbine blade is one of the most vulnerable parts of the damage of light-

ning. On the basis of a large number of research data, this report analyzes the

mechanism of the damage caused by lightning strike, sums up several lightning

protection measures of the blades of the wind turbine and introduces one inven-

tion patent. At the same time, the author introduces a simulated experiment

about the blade struck by lightning in Japan. It shows that the installation of

lightning arrester can effectively intercept lightning in the blade tip. Also, if the

lightning arrester is roughly the shape of a disk which installed on the surface

of the blade, it will engender electric arc inside.

19

References

[1] I.Cotton, B. McNiff, T. Soerenson, W. Zischank, P. Christiansen,

M.Hoppe-Kippler, S. Ramakers, P. Pettersson and E. Muljadi: ”Light-

ning Protection for Wind Turbines”, Proceedings of the 25th International

Conference on Lightning Protection (ICLP), (Rhodes,Greece), pp.848-853,

2000 .Wada et al.: ”Lightning Damages of Wind Turbine Blades in Win-

ter in Japan -Lightning Observation on the Nikaho-Kogen Wind Farm-”,

Proceedings of the 27th International Conference on Lightning Protec-

tion(ICLP), (Avignon,France), pp.947-952, 2004

[2] EC TR 61400-24, Wind turbine generator systems-Part 24:Lightning pro-

tection, 2002

[3] .Yokoyama, N.J.Vasa: ”Manner of Lightning Attachment to Non-

conductive Wind Turbine Blades”, Proceedings of the 27th International

Conference on Lightning Protection (ICLP), (Avignon,France), pp.936-

940, 2004

[4] akehiro Naka, Nilesh J. Vasa, Shigeru Yokoyama, Atsushi Wada, Akira

Asakawa, Hideki Honda, Kazuhisa Tsutsumi and Shinji Arinaga: ”Study

on Lightning Protection Methods for Wind Turbine Blades”, IEEJ Trans-

actions on Power and Energy, Vol.125, No.10, pp.993-999, 2005

20

References

[1] I.Cotton, B. McNiff, T. Soerenson, W. Zischank, P. Christiansen,

M.Hoppe-Kippler, S. Ramakers, P. Pettersson and E. Muljadi: ”Light-

ning Protection for Wind Turbines”, Proceedings of the 25th International

Conference on Lightning Protection (ICLP), (Rhodes,Greece), pp.848-853,

2000 .Wada et al.: ”Lightning Damages of Wind Turbine Blades in Win-

ter in Japan -Lightning Observation on the Nikaho-Kogen Wind Farm-”,

Proceedings of the 27th International Conference on Lightning Protec-

tion(ICLP), (Avignon,France), pp.947-952, 2004

[2] EC TR 61400-24, Wind turbine generator systems-Part 24:Lightning pro-

tection, 2002

[3] .Yokoyama, N.J.Vasa: ”Manner of Lightning Attachment to Non-

conductive Wind Turbine Blades”, Proceedings of the 27th International

Conference on Lightning Protection (ICLP), (Avignon,France), pp.936-

940, 2004

[4] akehiro Naka, Nilesh J. Vasa, Shigeru Yokoyama, Atsushi Wada, Akira

Asakawa, Hideki Honda, Kazuhisa Tsutsumi and Shinji Arinaga: ”Study

on Lightning Protection Methods for Wind Turbine Blades”, IEEJ Trans-

actions on Power and Energy, Vol.125, No.10, pp.993-999, 2005

21

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